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UCC256403: Maximum frequency setting at burst mode disable (option 7)

user5996000
Prodigy 60 points
Part Number: UCC256403

Hi expert, 

How to set the maximum frequency when the burst mode disable?

Which limit is applied BMTH or BMTL?

I want to limit the maximum frequency to stop hard switching.

thanks

yuki

  • 0
    TI__Mastermind 26215 points

    Hi Yuki-san,

    When BW is programmed to option 7, the BMTL thresholds become a minimum VTH-VTL switching threshold for VCR. Making the BMTL threshold to be larger, the maximum allowable switching frequency will become lower. Making the BMTL threshold to be smaller, the maximum allowable switching frequency will increase. 

    At light load, the VCR peak to peak will be dominated by the internal frequency compensation ramp. If you know the maximum switching frequency you need, you can estimate the needed BMTL threshold by calculating I=C*dV/dt where I is 2mA, C is the bottom VCR capacitor and dt is 1/2 the desired fsw period.

    Best Regards,

    Ben Lough